Tonsillar actinomycosis is a rare chronic disease that affects tonsillar tissue secondary to infection by anaerobic bacteria in the oral cavity. It usually presents as tonsillar hyperplasia and may mimic malignancy. We present the case of a patient referred from the pediatric department with severe unilateral tonsillar asymmetry with suspicion of malignancy. An imaging study showed tonsillar hyperplasia with no signs of local dissemination. The definitive diagnosis was made by excisional biopsy and histopathological study. An infectious disease evaluation indicated complementary treatment with high-dose penicillin-derived antibiotics, which achieved complete resolution of the clinical picture and no recurrent infections.